The major objectives are to delineate the specific actions of marihuana on short-term memory timing behavior, color perception and aggression. Since many investigators have employed rather insensitive techniques to measure the actions of marihuana on the above processes, it is planned to evaluate the effects of the drug from strong behavioral baselines such as those established with operant procedures. The basic paradigms we have included are (1) a covert memory task in which an S is required to avoid responding with an item previously presented, (2) a delayed matching to sample task which measures strength of short term memory at different delay intervals, (3) an experiment designed to determine the role of motivation on short term memory under marihuana, (4) a signal detection analysis of short term memory loss under marihuana, (5) an experiment designed to test marihuana's effect on the ability to judge recency in time (6) an experiment designed to assess timing behavior under marihuana via a temporally controlled operant, (7) a paradigm which measures visual perceptual alterations (changes in color perception) under marihuana via stimulus generalization tests along a wavelength continuum, (8) an experiment designed to assess the effect of marihuana on extinction-induced aggression.